Tetraethyl lead preparation



United States Patent 3,108,127 TETRAETHYL LEAD PREPARATION Laszlo F. Biritz, Chicago, Ill., assignor, by mesue assignments, to Houston Chemical Corporation, New York, N .Y., a corporation of Texas No Drawing. Filed Nov. 24, 1961, Ser. No. 154,818

15 Claims. (Cl. 260-437) The present invention relates to a process for manufacturing tetraethyl lead.

Tetraethyl lead is a valuable compound which has been manufactured on a large scale for many years. It is a relatively expensive material to manufacture. Accordingly, even slight improvements in yield, amounting to only a fraction of a percent, are important commercially and economically.

The conventional method for making tetraethyl lead today follows the equation:

It has been proposed in Pagliarini US. Patent 2,848,- 471, August 19, 1958, to catalyze this reaction with various aryl or mixed aryl alkyl phosphates. This procedure has the disadvantage of taking too long to get good yields.

It is an object of the present invention to provide a process of preparing tetraethyl lead which materially increases the speed of reaction Without decreasing the yield.

Another object is to provide a novel catalyst for the reaction of ethyl chloride with lead-monosodium alloy.

A further object is to decrease the byproduct formation in producing tetraethyl lead from ethyl chloride and leadsodium alloy. 1

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

It has now been found that these objects can be attained by reacting a lead-sodium alloy with ethyl chloride in the presence of a small amount, e.g., 0.002-10% based on the mols of sodium in the lead-sodium alloy, of hydrocarbon or haloaryl phosphites. The preferred phosphites are lower alkyl phosphites.

While preferably lead-monosodium alloy is employed, there can be used other lead-sodium alloys such as Na Pb and Na Pb The sodium can be 5-20% of the alloy by weight. The ethyl chloride and lead-sodium alloy can be reacted on an equimolar basis. However, preferably an excess of the ethyl chloride is used, e.g., 1.3- mols per mol of lead-monosodium alloy, to obtain better yields.

Examples of suitable phosphites which can be used as accelerators are trimethyl phosphite, triethyl phosphite, tripropyl pho-sphite, triisopropyl phosphite, tributyl phosphite, tri secondary butyl phosphite, tri tertiary butyl phosphite, propyl d-ibutyl phosphite, trihexyl phosphite, tridecyl phosphite, butyl diphenyl phosphite, diphenyl propyl phosphite, tridodecyl phosphite, tribenzyl phosphite, tri-allyl phosphite, trivinyl phosphite, trimethallyl phosphite, triphenyl phosphite, tri o-tolyl phosphite, tri p-tolyl phosphite, tri m-tolyl phosphite, tri p-butylphenyl phosphite, trixylyl phosphite, tri o-chlorophenyl phosphite, tri p-bromophenyl phosphite, tri a-naphthyl phosphite, tri f3- naphthyl phosphite.

The examples were carried out using the following conditions unless otherwise noted. \A 150ml. stainless steel bomb was purged with nitrogen (an inert atmosphere). Then 46 grams of lead-monosodium alloy (0.2 mol) of 12-24 mesh size were placed therein. The particle size of the alloy is conventional and is not critical. (Thus, it can be widely varied, e.g., from 4 to 300 mesh.) The bomb was evacuated to about 1 mm. or less and put in a Dry Ice-acetone bath and then there were condensed in the bomb grams of ethyl chloride. (This is a substantial excess of the ethyl chloride over theoretical and can be varied, for example, between 70 and grams, without significant change in yields.) The bomb was then pressured with nitrogen to 10 p.s.i. above atmospheric pressure. The phosphite catalyst (accelerator) was then put in the cold mixture and the bomb placed in a shaker bath maintained at about 70 C. It took about 3 minutes for the bomb to get to bath temperature. In the examples, in recording the time, the time to reach bath tem perature is included. Hence, the reaction time at the bath temperature was actually somewhat less than the times stated.

It may be noted that the-temperature of reaction is not critical but can be varied, e.g., from 50-120 C.

In the examples total yield was obtained by determining the amount of sodium chloride formed and yield of tetraethyl lead (T.E.L.) was determined by iodine titration.

As previously indicated, in the examples the alloy employed was lead-monosodiuxn alloy. The percent of catalyst in the examples is molar percent based on the mols of sodium in the alloy, e.g., if 2% catalyst is used in the example, there is 0.004 mol of catalyst (since 0.2 mol of alloy is employed in the examples unless otherwise noted).

A series of controls were run omitting the catalyst. It took 35-38 minutes to obtain a total yield of about and a T.E.L. yield of about 76% at a temperature of about 70-73" C. in these runs. Approximately 18-20% of the total yield was by-product rather than the desired tetraethyl lead.

Example 1 The catalyst employed was 2% of triisopropyl phosphite and the temperature of reaction was 70.5-70.8" C. There was a total yield of 94.6% and a T.E.L. yield of 83.20% in 18 minutes. This was a material reduction in time for completion of reaction and also was a reduction in side reaction from the 18-20% down to 12.07%. In contrast, certain other catalysts, e.g., tetraethyl orthosilicate and acetone, while reducing the time of reaction do not reduce the amount of side reaction.

The use of alkyl and aryl phosphates, while reducing the amount of side reaction in a manner analogous to that of the alkyl and aryl phosphites, take a longer time to complete the reaction. Thus, in experiments similar to Example 1 using 2% of catalyst it took 21 minutes with triethyl phosphate, 25 minutes with tributyl phosphate and 27 minutes with tricresyl phosphate to obtain comparable over-all yields and yields of T.E.L.

The difference in speed of reaction is further shown in the following comparison of times in minutes to obtain various total yields using 2% of triisopropyl phosphite and 2% triethyl phosphate at about 70 C.

The catalyst employed was 0.05% of triisopropyl phosphite in a large scale run at about 70 C. There was used 46 lbs. of ethyl chloride per lbs. of lead-monosodium alloy. The over-all yield and T.E.L. yield were of the same order as in Example 1 in the same time period.

3 Example 3 Utilizing 10% of triphenyl phosphite in the bomb described in connection with Example 1 there was a very rapid reaction which was complete in 17 minutes.

Example 4 Utilizing 2% of triphenyl phosphite in the bomb and an alloy which had been exposed to air there was obtained an over-all yield of 85.5% and a T.E.L. yield of 73.12% in 22 minutes. The exposing of the alloy to the atmosphere caused the reaction to go slower but did not affect the ratio of main product (T.E.L.) to by-product. It may be noted that in comparing total yield it is important to use the same catalyst at the same time.

Example 5 There was used 2% of triet-hyl phosphite in the bomb to obtain an over-all yield and a T.E.L. yield comparable to that utilizing trii-sopropyl phosphite in the same time period.

The present invention can be carried out either batchwise or in continuous fashion.

I claim:

1. A process of preparing tetraethyl lead comprising reacting a lead-sodium alloy and ethyl chloride in the presence of a catalyst selected from the group consisting of trihydrocarbon and trihalophenyl phosphites wherein the hydrocarbon groups are selected from the group consisting of alkyl, phenyl, alkyl phenyl, benzyl, naphthyl, vinyl, allyl and methallyl.

2. A process according to claim 1 wherein the catalyst is present in an amount of 0.002- mol percent based on the sodium in the alloy.

3. A process according to claim 2 wherein the leadsodium alloy is lead-monosodium alloy and the ethyl chlol ride is used in an amount in excess of that required to react with the alloy.

4. A process of preparing tetraethyl lead comprising reacting a lead-sodium alloy in the presence of a trialkyl phosphite as a catalyst.

5. A process according to claim 4 wherein the phosphite is a tri lower alkyl phosphite.

6. A process according to claim 5 wherein the phosphite is triisopropyl phosphite.

7. A process according to claim 4 wherein the alloy is lead-monosodium alloy and the catalyst is used in an amount of 0.002-2 mol percent based on the sodium in the alloy.

8. A process according to claim 4 wherein the phosphite is trimethyl phosphite.

9. A process according to claim 4 wherein the phosphite is triethyl phosphite.

10. A process according to claim 4 wherein the phosphite is tripropyl phosphite.

11. A process according to claim 4 wherein the phosphite is a tributyl phosphite.

12. A process of preparing tetraethyl lead comprising reacting lead-sodium alloy in the presence of a triaryl of the benzene series phosphite.

13. A process according to claim 12 wherein the phosphite is triphenyl phosphite.

14. A process according to claim 12 wherein the phosphite is a trialkyl phenyl phosphite.

15. A process according to claim 12 wherein the phosphite is tritolyl phosphite.

References Cited in the file of this patent UNITED STATES PATENTS 2,848,471 Pagliarini Aug. 19, 1958 

1. A PROCESS OF PREPARING TETRAETHYL LEAD COMPRISING REACTING A LEAD-SODIUM ALLOY AND ETHYL CHLORIDE IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF TRIHYDROCARBON AND TRIHALOPHENYL PHOSPHITES WHEREIN THE HYDROCARBON GROUPS ARE SELECTED FROM THE GROUP CONSISTING OF ALKYL, PHENYL, ALKYL PHENYL, BENZYL, NAPHTHYL, VINYL, ALKYL AND METHALLYL. 